Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1987-02-12
1989-05-02
Skudy, R.
Electrical generator or motor structure
Dynamoelectric
Rotary
310 91, 310154, 310185, 310258, H02K 118
Patent
active
048271730
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a commutator motor, especially a small motor for motor vehicles.
BACKGROUND OF THE INVENTION
Commutator motors of this type, because of the soft iron auxiliary poles that are provided, exhibit an inverse speed characteristic, which makes them suitable for use as drive motors for starters in motor vehicles or for blowers in vacuum cleaners.
In a known commutator motor of this type (U.S. Pat. No. 3,594,599), the soft iron auxiliary poles are secured with threaded bolts to the short-circuit ring, and the permanent-magnet poles are arrested by means of pressing springs on the side remote from the auxiliary poles, these pressing springs being secured to the short-circuit ring and pressing the permanent-magnet poles against the corresponding associated auxiliary pole. This kind of arresting of the permanent-magnet poles is necessary for positioning them, so that pole shifting cannot be caused by centrifugal and cross-field forces during commutator motor operation or by jarring when the commutator motor is not in operation, such as when it is being installed in the motor vehicle. Especially in commutator motors having a high number of poles, this kind of pole shifting would mean a wider range of deviation in terms of brush twisting. Yet deviations from optimal brush twisting lead to increased brush wear (at an overly large twisting angle), or in a worsening of efficiency (at too small a twisting angle). The fastening construction of the permanent-magnet poles as described in the known commutator motor is very expensive to assemble, however, and is unsuitable for large-scale mass production.
SUMMARY OF THE INVENTION
The commutator motor of the invention includes: a stator including a short-circuit annular member defining a longitudinal axis with the annular member having an inner wall surface. A rotor has an armature winding supported thereon and is rotatably mounted in the stator for rotation in a predetermined rotational direction. An even number of shell-like permanent-magnet poles have respective cross sections of a shape corresponding approximately to a segment of a cylinder and these permanent-magnet poles have curved outer surfaces facing away from the longitudinal axis and are arranged on the annular member so as to be evenly spaced at the same angle one from the other. Each of the permanent-magnet poles has a radially-extending first side edge defining the leading edge thereof with respect to said rotational direction and a second side edge defining the trailing edge thereof with respect to the rotational direction.
The commutator motor according to the invention further includes an even number of auxiliary poles made of ferromagnetic material and corresponding in number to the permanent-magnet poles. The auxiliary poles have respective side flanks and are arranged on the annular member so as to be directly at the leading edge of corresponding ones of the permanent-magnet poles. Bracing means are formed on the inner wall surface of the annular member to coact with the auxiliary poles for bracing the permanent-magnet poles against respective ones of the side flanks of the auxiliary poles with the curved outer surfaces thereof being in contact engagement with the inner wall surface.
The bracing means are a plurality of protrusions formed integrally with said annular member so as to extend inwardly toward the rotor from the inner wall surface of the annular member. The protrusions are disposed adjacent corresponding ones of the auxiliary poles so as to cause each of the permanent-magnet poles to be braced between one of the side flanks and one of the protrusions with the leading edge thereof being in abutment with the side flank of the auxiliary pole and the trailing edge thereof being in abutment with the protrusion. The protrusions can be in the form of a plurality of ribs, nose-like projections or bosses.
The short-circuit annular member defining the stator of the commutator motor has a predetermined length in the direction of its longitudinal axis a
REFERENCES:
patent: 3489937 (1970-01-01), Maher
patent: 3594599 (1971-07-01), West
patent: 4491756 (1985-01-01), Tomite
patent: 4542314 (1985-09-01), Corbach
Corbach Rainer
Mohr Adlof
Utsch Berthold
Zimmermann Kurt
Ottesen Walter
Robert & Bosch GmbH
Skudy R.
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